Hi all, I need some help with fuse size of my little array. I've searched this forum and others and answers seem to range from 'fuse to the wire size being used', 'go 25% above Isc of panel' or 'use appropriate size fuse'. What I do know so far is I should fuse each panel on the positive lead when paralleling three or more. I'm using three 120w Solar Cynergy panels:Voc - 21.0vIsc - 7.5aVmp - 17.0vImp - 7.0aconnected in parallel with #10 wire and y-connectors with MC4 ends. I was thinking of cutting up the y-connectors to make my own combiner box with a fuse from each '+' wire in box to '+' bus bar, '-' wires to '-' bus bar then 12 ft. of #6 wire from bus bars to my Morningstar SunSaver Duo controller. Sorry if over describing just trying to be clear, hopefully. Thanks for reading!

Multiply your Isc by 1.56. This gives you 11.7 amps. That would translate to a 12 amp fuse. The panels should say on them (in the same area you got your volt and amp ratings) their maximum series fuse size. I would go by that for sure.You will also need a fuse in the positive wire between your battery and your Morningstar; as close to the battery as possible. This will be based on the wire size. I would think you would run at least a #10 with this set up, a #8 would be better. With a #8 I'd use a 40 amp fuse.

No fuse on any of them between panels and controller they are in parallel on. You would fuse if you had three in series sized to the "series fuse" rating.You should have a fuse on the positive wire between controller and battery though, near the battery.

No fuse IMO. But find the "series fuse rating" from Solar Cynergy.The series fuse rating is probably 15 amps. Since the other two panels combined do not exceed the rating no fuse is needed. But again you need to verify the rating.Panels -> combiner box -> 12v switch -> controller -> switch -> 30a fuse -> battery.

If it were mine I would individually fuse each panel. If one goes out the other two would still be functional. Normally fuses are chosen for twice the normally expected full current. So if your normal max is 12A, fuse at 25A.Everyone causes happiness. Some when they come in, and some when they leave.

Here is the correct info--wade down to the strings fusing parthttp://www1.cooperbussmann.com/pdf/9df1f7ec-8c62-4210-8cf8-9504927394f0.pdf

Proper Fusing Of Three Parallel Panels | Good Sam Community

BFL13
Explorer II
Apr 10, 2014
Here is the correct info--wade down to the strings fusing part

http://www1.cooperbussmann.com/pdf/9df1f7ec-8c62-4210-8cf8-9504927394f0.pdf
Gonzo42
Explorer
Apr 10, 2014
If it were mine I would individually fuse each panel. If one goes out the other two would still be functional. Normally fuses are chosen for twice the normally expected full current. So if your normal max is 12A, fuse at 25A.

Everyone causes happiness. Some when they come in, and some when they leave.
time2roll
Nomad
Apr 10, 2014
No fuse IMO. But find the "series fuse rating" from Solar Cynergy.

The series fuse rating is probably 15 amps. Since the other two panels combined do not exceed the rating no fuse is needed. But again you need to verify the rating.

Panels -> combiner box -> 12v switch -> controller -> switch -> 30a fuse -> battery.
BFL13
Explorer II
Apr 10, 2014
No fuse on any of them between panels and controller they are in parallel on. You would fuse if you had three in series sized to the "series fuse" rating.

You should have a fuse on the positive wire between controller and battery though, near the battery.
KD4UPL
Explorer
Apr 10, 2014
Multiply your Isc by 1.56. This gives you 11.7 amps. That would translate to a 12 amp fuse. The panels should say on them (in the same area you got your volt and amp ratings) their maximum series fuse size. I would go by that for sure.
You will also need a fuse in the positive wire between your battery and your Morningstar; as close to the battery as possible. This will be based on the wire size. I would think you would run at least a #10 with this set up, a #8 would be better. With a #8 I'd use a 40 amp fuse.

Forum Discussion

Proper Fusing Of Three Parallel Panels

About Technical Issues

Related Content

Proper outside storage

Proper Cheese

Winnebago Fuse

Proper Hydraulic Fluid to use?

Fuses